Work vehicles such as backhoes, cranes, and excavators often need to both travel over the ground and travel on roads in order to get to and from work sites. To travel over the road, they must be supported on wheeled suspensions and have a relatively narrow chassis. Yet to work effectively in the field they should have a wide base of support and be relatively rigidly connected to the ground to resist pitching, rolling and yawing.
Vehicles such as those named above are of particular concern since they have arms that reach far out away from the vehicle chassis to either carry loads or to dig into the ground with ground engaging tools such as pavement breakers or buckets. Without a solid supporting foundation, these outwardly reaching arms might overbalance the vehicle resting on its tires.
The historical method of providing both roadability and a solid foundation for working has been to add stabilizers that are slidingly or pivotally coupled to the chassis of the vehicle and extend outward therefrom to engage the ground. These stabilizers typically include an elongated member to which a broad ground-engaging pad is fixed at a free lower end thereof.
These stabilizers are commonly moved by actuators such as hydraulic cylinders that in turn are coupled to electrical, hydraulic or electro-hydraulic control circuits. The operator typically has a manual operator control or input device such as a switch, a lever or a joystick that he manipulates to extend or retract the cylinders, thereby lowering or raising the stabilizers.
When the operator manipulates the controls to lower the stabilizer, the stabilizer typically slides or pivots downward and outward until the stabilizer pad engages the ground. Once in this position, the operator can lower the stabilizer a little further, lifting the chassis of the vehicle slightly, raising it a bit off its wheels.
This transfers some of the weight of the vehicle to the stabilizers and converts the vehicle's chassis into a solid, fixed platform with a broader base of support than its wheels alone could provide.
Once in this stabilized position, the operator can manipulate the vehicle's attachments with confidence that the vehicle will not pitch, roll or tip.
In many operations the vehicle in question must be moved with some regularity. For example, backhoes are often used to clean ditches on the side of the road.
To do this cleaning, they are moved to a position facing the ditch. The stabilizers are then lowered to engage the ground. The operator then manipulates the backhoes' jointed arm (the boom, dipper and bucket) to scoop out material from the ditch.
After a few scoops, the operator stops digging, lifts the stabilizers, moves the backhoe forward and then backward to one side of his original position. He again lowers the stabilizers and again takes a few scoops with the vehicle's bucket.
The process may repeat perhaps 20–100 times in the course of a day as the backhoe gradually goes down the ditch alongside the road cleaning excess dirt from it.
The raising and lowering of the backhoe is time consuming during these operations. In current designs, the operator must keep his hands on the stabilizer lift and lower controls the entire time the stabilizers are being lifted and lowered. This is time that he could spend rotating his seat to a forward facing position, shifting the vehicle into a drive gear and moving the vehicle a few feet down the road. Furthermore, if he becomes careless with the repetitive stabilizer lifting and lowering, he may keep the stabilizer controls in the lift position too long. On some vehicles with stabilizers, holding the control in the lift position after the stabilizer is already raised can cause the vehicle's engine to stall.
What is needed, therefore, is a work vehicle having an improved stabilizer control circuit that can relieve the operator of the need to continually engage the controls the keep the stabilizers moving.
What is also needed is a system that can distinguish between an operators signal to raise or lower the stabilizer slightly and a signal to raise the stabilizer completely and automatically.
What is also needed is a system that can sense when the stabilizer is completely raised and responsively shut off the flow of fluid to and from the stabilizer hydraulic cylinders.
It is an object of this invention to provide one or more of the foregoing features and advantages in one or more of the embodiments claimed below.